Leakage current reduction in a power regulator

ABSTRACT

A regulator with decreased leakage and low loss for a power amplifier is described. Switching circuitry is used to connect the regulator input bias to a bias control voltage when the power amplifier is to be operated in an on condition or to a voltage generator when the power amplifier is to be operated in an off condition.

BACKGROUND

1. Field

The present teachings relate to power regulators. More particularly, thepresent teachings relates to leakage current reduction methods andapparatus in a power regulator.

2. Description of Related Art

Mobile communication devices such as mobile telephones are generallypowered by batteries. Therefore, it is desirable to improve the timebefore the battery charge is depleted. One method of improving batterylife is to reduce the unintended current leakage from power supply toelectrical ground or other reference voltage in the radio. By reducingthis wasted current, the useful time of the battery is increased.Integrated circuit power amplifiers often have a regulator function thatadjusts the output power of the amplifier. In order to further conservepower, these power amplifiers are turned off when the radio is nottransmitting.

When a power amplifier is operated in an OFF state, the regulator shutsoff the power to the amplifier and it is desirable to shut off thecurrent flow through the regulator to as close to zero current aspossible. Conversely, when it is operated in an ON state, it isdesirable for the regulator to have as little loss or voltage drop aspossible to maximize power efficiency of the system.

An optimal regulator will therefore have very low leakage when OFF andvery low loss when ON. One way to achieve low loss in the ON state is touse MOS transistors having low threshold voltage. When transistors withlow threshold voltage are used, the “on” resistance of those transistorsis decreased when they are operated in the ON state as compared totransistors having higher threshold voltage.

However, when MOS transistors of low threshold voltage are used in aregulator, and they are operated in the OFF state, they may have higherleakage current from source to drain because they are still insubthreshold operation when the gate to source voltage Vgs is equal tozero. Transistors with higher threshold voltage generally have lowerleakage in the OFF state than transistors of lower threshold voltage.

As a mitigation effort to reduce leakage from source to drain in theregulator transistors, an increase in the drawn channel length may beattempted. However, increasing the channel length of the regulatortransistors has only a weak effect on the leakage current and has asignificant reduction of efficiency due to increased “on” resistance.The need for a low-leakage, high-efficiency regulator circuit is clear.

FIG. 1 shows Vgs as a function of log(Ids) for a MOS transistor. Insub-threshold operation, the dependency of Vgs on log(Ids) is linear.Two different points P1 and P2 are taken on the sub-threshold portion ofthe curve, to define a ΔVgs and a ΔlogIds. A sub-threshold swing S canbe defined as the reciprocal of the slope ΔlogIds/ΔVgs, i.e.S=ΔVgs/ΔlogIds. S is usually measured in millivolts per decade ofΔlogIds, i.e. mV/decade. For example, a sub-threshold swing S of 100mV/decade means that a change in Vgs of 100 mV will result in a changein Ids of one decade (10×).

FIG. 2 shows a prior art arrangement of a power amplifier with voltageregulator. The voltage regulator of FIG. 2 comprises a p-channel MOS(202) located on top of a power amplifier PA (250). Regulator transistor(202) regulates the voltage output Vout_reg (206) of the power amplifier(250). Regulator transistor (202) can be in an ON condition—power supplyVdd (208) connected with the power amplifier (250)—or an OFFcondition—power supply Vdd (208) disconnected from the power amplifier(250). The voltage signal Vbias (204) biases the regulator transistor(202) into the ON condition or the OFF condition.

In particular, when Vbias (204) increases towards the power supply Vdd(208), regulator transistor (202) starts to turn off, increasing its“on” resistance. As the “on” resistance of regulator transistor (202)increases, its source to drain voltage Vds increases. This causes adecrease in the regulated voltage output Vout_reg (206). The decrease inVout_reg (206) reduces the amplification of the power amplifier (250).Conversely, when Vbias (204) decreases towards Vref (210), the regulatortransistor (202) turns on, reducing its “on” resistance, therebydecreasing its Vds and increasing Vout_reg (206). This results in higheramplification of the power amplifier (250).

When the regulator transistor (202) is biased into the OFF condition,the Vgs of regulator transistor (202) is typically 0V, because the gateinput voltage Vbias (204) is set to the power supply Vdd. If thep-channel regulator transistor (202) has a threshold voltage of 0.4V anda sub-threshold swing of 100 mV/decade, then the transistor (202) ispassing a subthreshold current Ids at a current value of 4 decades belowthreshold.

Regulator transistors are typically very wide (in terms of the distanceperpendicular to the current flow direction in the transistor), in orderto minimize their resistance in the ON state. As an example, it can beassumed that the regulator transistor (202) has a total width of 100 mmand passes current at a rate of 20 mA per millimeter of width atthreshold. Then the total current in the OFF condition is 100 mm×20mA/mm width×1E−4=200 μA. A leakage current of 200 μA in the OFFcondition is a significant battery drain and would be too high forpractical use.

SUMMARY

According to a first aspect, an arrangement for reducing leakage currentin a regulator transistor for a power amplifier is provided, comprising:a switching arrangement to switch a biasing input of the regulatortransistor between a first condition where the regulator transistor isbiased by an input voltage to the regulator transistor during an ONstate of the regulator transistor and a second condition where theregulator transistor is biased by a leakage current reduction voltageduring an OFF state of the regulator transistor, wherein, during the OFFstate of the regulator transistor, a sub-threshold biasing voltage ofthe regulator transistor is controllably distanced from a thresholdvoltage Vth of the regulator transistor by controlling the leakagecurrent reduction voltage.

According to a second aspect, a leakage current reduction circuit isprovided, comprising: (a) a regulator transistor comprising an inputadapted to bias the regulator transistor in an ON condition, as soon asan activation voltage reaches a threshold value, or an OFF condition;and (b) switching means connected with the input to connect the inputwith a first voltage during the ON condition and a second voltage duringthe OFF condition, wherein, in the OFF condition, a voltage distancebetween the activation voltage and the threshold value is higher than anabsolute value of the threshold value.

According to a third aspect, a voltage generator is provided,comprising: (a) an input adapted to be driven by an input waveform; (b)means to generate, along two distinct paths, complementary waveformsbased on the input waveform; (c) a rectifying arrangement to rectify thecomplementary waveforms to obtain a rectified voltage, switching statusof the rectifying arrangement being driven by the complementarywaveforms themselves; and (d) means to limit the rectified voltage to acontrollable voltage value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing log(Ids) as a function of Vgs, in order todefine transistor sub-threshold swing.

FIG. 2 shows a prior art arrangement of a power amplifier with voltageregulator.

FIG. 3 shows an arrangement of a power amplifier with voltage regulatoraccording to an embodiment of the present disclosure.

FIG. 4 shows one embodiment of the positive voltage generator (PVG)described in FIG. 3.

FIG. 5 shows a further arrangement of a power amplifier with voltageregulator according to a further embodiment of the present disclosure.

FIG. 6 shows one embodiment of the negative voltage generator (NVG)described in FIG. 5.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

Throughout this description, embodiments and variations are describedfor the purpose of illustrating uses and implementations of theinventive concept. The illustrative description should be understood aspresenting examples of the inventive concept, rather than as limitingthe scope of the concept as disclosed herein.

FIG. 3 shows a circuital arrangement according to an embodiment of thepresent disclosure. In particular, FIG. 3 shows a simplified blockdiagram of a power amplifier PA (350) with regulator transistors M1(302) and M2 (304). In addition to the power amplifier and regulatortransistor shown in FIG. 2, a positive voltage generator block PVG (318)and switching logic (316, 320, 322, 324) are included in the circuit ofFIG. 3.

According to the embodiment of FIG. 3, a gate input voltage (306) of ap-channel regulator transistor M1 (302) is provided either by PVG (318)or by the op amp (330). The choice of input to be provided to theregulator transistor M1 (302) is made by a transistor (316) and a passgate (322). In particular, when the power amplifier PA (350) is biasedin an OFF state, the pass gate (322) disconnects the gate input Vbias1(306) from the output of the op amp (230) and the transistor (316)connects it to the output (314) of the PVG (318).

In the embodiment of FIG. 3, the PVG (318) provides a positive biasVdd+ΔV that is higher than the power supply Vdd (312). By way ofexample, ΔV can be selected to be equal to the threshold voltage of M1,e.g., 0.4V. If the PVG output voltage (314) is 0.4V higher than thepower supply (312), then the Vgs of the regulator transistor M1 (302) is+0.4V. Given that the regulator transistor M1 (302) comprises ap-channel transistor in the present embodiment, the Vgs values forbiasing such transistor in the ON state comprise negative values.Therefore, a +0.4V Vgs value turns off M1 (302) by an additional 0.4V.While this does not affect the OFF status of M1 (302), it advantageouslyaffects its leakage current. In particular, assuming that M1 (302) has asubthreshold swing S=100 mV/decade, the leakage current of M1 (302) isreduced by 4 orders of magnitude. Therefore, such reduction provides thetransistor M1 (302) with an acceptable level of leakage during its OFFstate. The person skilled in the art of electronics design, andparticularly in the power amplifier design arts, will understand, uponreview of the present teachings, that the amount of leakage current ofM1 can be controlled via the selection of the value ΔV.

The operation of the switching logic (316, 320, 322, 324) is nowdescribed in more detail. In particular, two complementary logic controlsignals, Vctrl (324) and Vctrl_b (320) are provided in order to causethe pass gate (322) to switch. In the embodiment of FIG. 3, the pass ortransmission gate (322) comprises a combination of an n-channel MOStransistor (upper transistor in FIG. 3) and a p-channel MOS transistor(lower transistor in FIG. 3). The control voltages Vctrl (324) andVctrl_b (320) are provided by circuitry not shown in this figure usingmeans well known to those skilled in the circuit design arts. Vctrl(324) is typically allowed to vary in value from supply voltage Vdd(312) to a value near Vdd/2. Vctrl_b (320) varies in a complementary oropposite manner to Vctrl (324).

Therefore, when Vctrl (324) is in digital “high” state (for example,when it is equal to Vdd (312)), Vctrl_b (320) is lower and close toVdd/2 in this particular implementation. In contrast, when Vctrl (324)is in a digital “low” state (for example, close to Vdd/2), then Vctrl_b(320) is high.

When it is desired to operate the power amplifier (350) in the OFFstate, the digital control voltage Vctrl (324) is provided to the gateof the p-channel transistor of the pass gate (322) in the high state.When Vctrl (324) is in the high state, it turns off the p-channeltransistor of the pass gate (322). At the same time, Vctrl_b (320),which is low, turns off the n-channel transistor of the pass gate (322)and turns on the p-channel transistor (316). In this state, the passgate (322) disconnects the gate input Vbias1 (306) from the output ofthe op amp (330), and Vbias1 (306) is coupled to the output (314) of thePVG (318) through the transistor (316). As described above, thiscondition turns off the regulator transistor M1 (302), therebydisconnecting the power supply Vdd (312) from the power amplifier (350).

When the power amplifier (350) is desired to operate in the ON state,the digital control voltage Vctrl (324) is provided to the gate of thep-channel transistor of the pass gate (322) in the low state. When Vctrl(324) is in the low state, it turns on the p-channel transistor of thepass gate (322). At the same time, Vctrl_b (320), which is high, turnson the n-channel transistor of the pass gate (322) and turns off thep-channel transistor (316). In this state, the pass gate (322) connectsthe gate input Vbias1 (306) to the output of the op amp (330), andVbias1 (306) is disconnected from the output (314) of the PVG (318). Theoutput of the op amp (330) is indicative of the difference between asignal Vfb (332) and a signal Vramp (328). The signal Vfb (332) isindicative of the regulated voltage Vout_reg (310) as shown by thefeedback path connecting Vout_reg (310) to Vfb (332) through voltagedivider (326).

Therefore, Vfb (332) is a scaled version of Vout_reg (310) set by sizingthe resistors in the voltage divider (326). The op amp (330) comparesVramp (328) to Vfb (332) and drives Vbias1 (306) such that regulatortransistor M1 (302) drops a voltage level below Vdd (312) to properlyset Vout_reg (310). The maximum output power level occurs when Vout_regapproaches Vdd. A typical range for the Vramp (328) control signal is0.1-1.75V and the typical battery voltage Vdd is 3.5V. Therefore, theregulator loop can be designed such that the ratio between Vout_reg andVramp is 3.5/1.75 or 2, set by the resistive divider (326).

Due to reliability constraints, semiconductor processes typically have aspecified maximum voltage that is allowed to exist from a source todrain across a transistor (“Max Vds”). When the difference in potentialbetween power supply (e.g., battery supply) Vdd (312) and Vref (334) isless than the Max Vds of the regulator transistor (302), a singletransistor M1 (302) is sufficient to prevent violation of the this MaxVds rule in the regulator block.

Therefore, in one embodiment, the regulator transistor M2 (304) isreplaced with a direct electrical connection disposed between the drainof the regulator transistor M1 (302) and Vout_reg (310). In such anembodiment, when the regulator transistor M1 (302) is biased in the OFFcondition, the entire potential Vdd-Vref is applied as the Vds acrossthat transistor.

In another embodiment, when the difference in potential between thepower supply Vdd (312) and Vref (334) exceeds Max Vds of the transistorM1 (302), the regulator transistor M2 (304) can be coupled as shown inFIG. 3 between the drain of the regulator transistor M1 (302) and theVout_reg (310). The gate input Vbias2 (308) of the regulator transistorM2 (304) is, in one embodiment, equal to half of the power supply Vdd.When Vbias2 (308) equals half of the power supply Vdd and the regulatortransistor M1 (302) is biased in the OFF condition, the power supplyvoltage Vdd is shared equally across the regulator transistors M1 (302)and M2 (304), thereby doubling the maximum power supply that theregulator transistors can reliably handle. As one of ordinary skill inthe art of electronic circuit design will appreciate, additionalregulator transistors can be coupled in series to further increase thevoltage handling capability of the regulator.

While the embodiment of FIG. 3 shows the regulator transistors ascomprising p-channel MOS transistors, persons skilled in the electronicsdesign arts will appreciate that the concepts set forth in the presentdisclosure are applicable to circuits having regulator transistorscomprising other electronic devices, e.g., comprising n-channel MOStransistors. Such additional embodiment will be explained with referenceto FIG. 5 and FIG. 6, later discussed. For example, in FIG. 5, theoutput (514) of a negative voltage generator NVG (518) is Vref−ΔV, thusfurther biasing M2 in the OFF condition, given that in this example itsVgs is equal to −ΔV.

FIG. 4 shows one embodiment of the positive voltage generator (PVG)described above with reference to FIG. 3. As shown in FIG. 4, the inputVin (402) of the PVG is driven by a low power square waveform (404)generator. Inverters Inv1 (406) and Inv2 (408) generate complementarywaveforms along respective circuit paths (410), (416). The voltageacross inverters Inv1 (406) and Inv2 (408) may be limited by p-channelMOS transistor M3 (434) and its gate input signal Vbias3 (436), in orderto avoid violating the “Max Vds” limit on Inv1 (406) and Inv2 (408). Afurther current adjustment of the PVG can be obtained by adjusting thefrequency of the input waveform (404).

Each waveform is coupled, along the paths (416) and (410), throughrespective capacitors C1 (418) and C2 (420), to a rectifying arrangementincluding switching transistors M4 through M7 (422, 424, 426 and 428).In accordance with the embodiment shown in FIG. 4, the gates of theswitching transistors are driven by the coupled waveforms themselves inorder to perform the switching action, and are therefore driven withoutneed for a separate gate drive for the switches. In particular,according to the embodiment shown in FIG. 4, the switch M4 comprises ann-channel MOS transistor that couples the signal Vdd (412) to path (416)when the signal on path (410) is a logic “high”. The switch M5 comprisesan n-channel MOS transistor that couples the signal Vdd (412) to thepath (437) when the signal on path (416) is a logic “high”. The switchM6 comprises a p-channel MOS transistor that allows the signal on thepath (437) to be transmitted to the output when the signal on the path(416) is a logic “low”. The switch M7 comprises a p-channel MOStransistor that allows the signal on the path (416) to be transmitted tothe output when the signal on path (410) is a logic “low”.

As shown in FIG. 4, the rectified voltage output (414) (see the voltageoutput (314) described above and shown in FIG. 3) is stored and filteredby capacitor C3 (430). A diode connected transistor M8 (432) acts as avoltage limiter that limits the output of the PVG to the supply (e.g.,battery) voltage Vdd+one Vds=Vgs=ΔV that is approximately equal to thethreshold voltage of device M8 (432). The value ΔV is controllable. Forexample, different values of ΔV may be obtained by varying the devicesused to implement the transistor M8 (432).

The combined switching and driving arrangement shown in FIG. 4 resultsin a single supply voltage Vdd across any of the devices. This featurefacilitates the use of single devices (i.e., there is no need ofstacked-connected in series—devices to handle a higher Vds voltage) inthe charge pump circuit of FIG. 4, thus increasing efficiency anddecreasing current consumption. For example, if two devices in serieshad to be used for each switch in the charge pump to handle theexcessive Vds voltage, the gate capacitance of the switches wouldincrease due to larger devices needed for the same switch resistance (asobtained when using only one device). Larger gate capacitance wouldresult in larger driving current, thus decreasing the efficiency of thecharge pump.

According to a practically implemented embodiment of the charge pump,the charge pump had a current consumption of 0.25 μA operating atseveral hundred 15 Kilohertz.

As already noted above, the embodiment of FIG. 5 shows a negativevoltage generator NVG (518) and n-channel MOS transistors M1 (502) andM2 (504). The operation of the embodiment of FIG. 5 will be brieflyexplained below. The person skilled in the art will understand that thestructure and the operation can be also understood from the descriptionof the PVG and p-channel MOS embodiment described above with referenceto FIG. 3.

As shown in FIG. 5, NVG (518) generates a voltage (514) equal to Vref−ΔVthat is lower than the reference voltage Vref. By way of example, ΔV canbe selected to equal to the threshold voltage of MIB, e.g., 0.4V.

Similarly to what explained with reference to FIG. 3, switchingarrangement A of FIG. 5 disconnects the steering op amp (530) during apower down condition and switching arrangement B of FIG. 5 connects theNVG voltage (514) to the gate of the pass device M1 (502) of theregulator of FIG. 5.

Also in the embodiment of FIG. 5, similarly to what shown in theembodiment of FIG. 3, Vbias2 (508) can be adjusted to provide equalvoltage division between devices M1 (502) and M2 (504).

Should Vout_reg (510) be adjusted to close to Vdd, the voltage output ofop amp (530) should be above Vdd.

Similarly to what shown in FIG. 4, FIG. 6 shows one embodiment of thenegative voltage generator (NVG) described above with reference to FIG.5. Also in this case, the person skilled in the art will understand thatthe structure and operation of the NVG of FIG. 6 can be understood fromthe description of the PVG provided in FIG. 4.

Inverters Inv1 (606), Inv2 (608), capacitors C1 (618), C2 (620), andtransistors M4 (622) and M5 (624) act as level shifters that outputcomplementary square waveforms at nodes (616) and (637) of value Vref toVref-Vsup. This waveform is rectified by switches M7 (632) and M6 (626)that are self driven from the same waveforms but opposite phases.Transistor M8 (633) acts as a negative voltage limiter and capacitor C3(630) performs a storage and filtering function. Transistor M3 (634)together with its gate input Vbias3 (636) limits the Vsup voltage inorder to avoid violating the “max Vds” limit on Inv1 (606) and Inv2(608).

The devices according to the present disclosure can also be used, by wayof example, with power amplifiers present in amplitude modulators, suchas those found in EDGE type GSM radios.

Accordingly, what has been shown are devices and methods for leakagecurrent reduction in a power regulator. While the devices and methodshave been described by means of specific embodiments and applicationsthereof, it is understood that numerous modifications and variationscould be made thereto by those skilled in the art without departing fromthe spirit and scope of the disclosure. It is therefore to be understoodthat within the scope of the claims, the disclosure may be practicedotherwise than as specifically described herein

A number of embodiments of the present inventive concept have beendescribed. Nevertheless, it will be understood that variousmodifications may be made without departing from the scope of theinventive teachings. For example, also integrated CMOS regulators can beused with the inventive concepts taught in the present disclosure, bothin the PVG and NVG embodiments.

Accordingly, it is to be understood that the inventive concept is not tobe limited by the specific illustrated embodiments, but only by thescope of the appended claims. The description may provide examples ofsimilar features as are recited in the claims, but it should not beassumed that such similar features are identical to those in the claimsunless such identity is essential to comprehend the scope of the claim.In some instances the intended distinction between claim features anddescription features is underscored by using slightly differentterminology.

1. An arrangement for reducing leakage current in a regulator transistorfor a power amplifier, comprising: a switching arrangement to switch abiasing input of the regulator transistor between a first conditionwhere the regulator transistor is biased by an input voltage to theregulator transistor during an ON state of the regulator transistor anda second condition where the regulator transistor is biased by a leakagecurrent reduction voltage during an OFF state of the regulatortransistor, wherein, during the OFF state of the regulator transistor, asub-threshold biasing voltage of the regulator transistor iscontrollably distanced from a threshold voltage Vth of the regulatortransistor by controlling the leakage current reduction voltage.
 2. Thearrangement of claim 1, wherein the regulator transistor is connectedwith a supply voltage and the leakage current reduction voltage differsfrom the supply voltage by a controllable voltage amount ΔV, thusdistancing the sub-threshold biasing voltage of the regulator transistorfrom the threshold voltage Vth of the regulator transistor by an amountVth+ΔV.
 3. The arrangement of claim 2, wherein the leakage currentreduction voltage is a positive voltage.
 4. The arrangement of claim 1,wherein the regulator transistor is connected with a supply voltage andthe leakage current reduction voltage differs from a reference voltageby a controllable amount ΔV, thus distancing the sub-threshold biasingvoltage of the regulator transistor from the threshold voltage Vth ofthe regulator transistor by an amount Vth+ΔV.
 5. The arrangement ofclaim 4, wherein the leakage current reduction voltage is a negativevoltage.
 6. The arrangement of claim 1, wherein ΔV=Vth, thus distancingthe sub-threshold biasing voltage of the regulator transistor from thethreshold voltage Vth of the regulator transistor by an amount 2 Vth. 7.The arrangement of claim 1, wherein the switching arrangement comprisesa switching transistor selectively connecting the biasing input of theregulator transistor with the input voltage or the leakage currentreduction voltage.
 8. The arrangement of claim 7, wherein the switchingtransistor is a pass gate transistor.
 9. The arrangement of claim 7,wherein the switching transistor is controlled by two complementarysignals so that the first condition is obtained through activation of afirst signal of the two complementary signals and the second conditionis obtained through activation of the second signal of the twocomplementary signals.
 10. The arrangement of claim 7, furthercomprising a further switch connected with the leakage current reductionvoltage and between the switching transistor and the biasing input ofthe regulator transistor, the further switch being synchronous with theswitching transistor, the further switch connecting the regulatortransistor with the leakage current reduction voltage during the secondcondition and disconnecting the regulator transistor from the leakagecurrent reduction voltage during the first condition.
 11. Thearrangement of claim 10, wherein the further switch is a furthertransistor switch.
 12. The arrangement of claim 1, further comprising apositive voltage generator, the positive voltage generator connectedwith a supply voltage and outputting the leakage current reductionvoltage.
 13. The arrangement of claim 1, further comprising a negativevoltage generator, the negative voltage generator connected with asupply voltage and outputting the leakage current reduction voltage. 14.The arrangement of claim 1, further comprising the regulator transistor.15. A power amplifier comprising the arrangement of claim 12, the poweramplifier being connected to the regulator transistor.
 16. A poweramplifier comprising the arrangement of claim 13, the power amplifierbeing connected to the regulator transistor.
 17. A leakage currentreduction circuit comprising: (a) a regulator transistor comprising aninput adapted to bias the regulator transistor in an ON condition, assoon as an activation voltage reaches a threshold value, or an OFFcondition; and (b) switching means connected with the input to connectthe input with a first voltage during the ON condition and a secondvoltage during the OFF condition, wherein, in the OFF condition, avoltage distance between the activation voltage and the threshold valueis higher than an absolute value of the threshold value.
 18. The leakagecurrent reduction circuit of claim 17, wherein the voltage distance isequal to two times the absolute value of the threshold value.
 19. Theleakage current reduction circuit of claim 17, wherein the voltagedistance is controllable by controlling the second voltage.
 20. Theleakage current reduction circuit of claim 17, wherein the regulatortransistor is connected with a power supply voltage and the secondvoltage is equal to the power supply voltage plus a controllable voltagevalue.
 21. The leakage current reduction circuit of claim 20, whereinthe second voltage is a positive voltage.
 22. The leakage currentreduction circuit of claim 17, wherein the second voltage is equal to areference voltage minus a controllable voltage value.
 23. The leakagecurrent reduction circuit of claim 22, wherein the second voltage is anegative voltage.
 24. A voltage generator comprising: (a) an inputadapted to be driven by an input waveform; (b) means to generate, alongtwo distinct paths, complementary waveforms based on the input waveform;(c) a rectifying arrangement to rectify the complementary waveforms toobtain a rectified voltage, switching status of the rectifyingarrangement being driven by the complementary waveforms themselves; and(d) means to limit the rectified voltage to a controllable voltagevalue.
 25. The voltage generator of claim 24, the voltage generatorbeing for reducing leakage current in a regulator transistor.
 26. Thevoltage generator of claim 25, the voltage generator being connectedwith the arrangement of claim 1, the voltage generator being furtherconnected with a voltage supply and outputting the leakage currentreduction voltage.
 27. The voltage generator of claim 24, wherein themeans to generate the complementary waveforms comprise a first inverterand a second inverter.
 28. The voltage generator of claim 27, furthercomprising: voltage limiting means to limit the voltage across the firstinverter and the second inverter.
 29. The voltage generator of claim 24,further comprising current adjusting means to adjust current throughputthrough the voltage generator.
 30. The voltage generator of claim 24,wherein the rectifying arrangement comprises switching capacitors andswitching transistors.
 31. The voltage generator of claim 24, whereinthe means to limit the rectified voltage to a controllable voltage valuecomprise a transistor acting as a voltage limiter.
 32. The voltagegenerator of claim 24, said voltage generator being a positive voltagegenerator.
 33. The voltage generator of claim 24, said voltage generatorbeing a negative voltage generator.